An 1802 UTC GOES-17 “Red” Visible (0.64 µm) image with an overlay of the 12 UTC surface analysis (above) revealed a well-defined rope cloud which stretched for nearly 1000 miles, marking the cold front position at the time of the image. Rope clouds can therefore be used to diagnose the exact location of the leading edge of a cold frontal boundary between times when surface analyses are available. In this case, the cold front was associated with a Hurricane Force low over the East Pacific Ocean on 16 January 2019 (surface analyses).

GOES-17 “Red” Visible (0.64 µm) images [click to play animation]

An animation of GOES-17 Visible images is shown above, with a zoomed-in version closer to the rope cloud displayed below.

GOES-17 “Red” Visible (0.64 µm) images [click to play animation]

An even closer look (below) showed that the rope cloud was only about 2-3 miles wide.

GOES-17 “Red” Visible (0.64 µm) images [click to enlarge]

When the 18 UTC surface analysis later became available, a close-up comparison with the 1802 UTC GOES-17 Visible image (below) indicated that the northern portion of the cold front (as indicated by the rope cloud) was slightly ahead of — and the southern portion slightly behind — the smoothed cold frontal position of the surface analysis product.

1-km resolution AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images of the rope cloud were captured by NOAA-15 at 1617 UTC (above) and by NOAA-18 at 1710 UTC (below). Along the northeastern portion of the rope cloud, there were a few convective clouds which exhibited cloud-top infrared brightness temperatures as cold as -55 to -60ºC (darker shades of red) and were tall enough to be casting shadows due to the low morning sun angle.

On the following day, another rope cloud (one that was more fractured) was seen moving across Hawai’i as a cold front passed the island of Kaua’i — the southeastward progression of the rope cloud was evident on GOES-17 True Color Red-Green-Blue (RGB) images (above) from the UW AOS site.

Surface observations plotted on GOES-17 Visible images (below) showed the wind shift from southwest to north as the cold front moved through Lihue on Kauwa’i around 00 UTC.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image, with and without buoy observations [click to enlarge]

Not all rope clouds are associated with cold fronts; with ample illumination from the Moon — in the Waxing Gibbous phase, at 90% of Full — a Suomi NPP VIIRS Day/Night Band (0.7 µm) image (above) provided a “visible image at night” of a rope cloud in the northern Gulf of Mexico which highlighted a surface wind shift axis.

A sequence of VIIRS Day/Night Band images from NOAA-20 and Suomi NPP (below) showed the movement of the rope cloud during a time span of about 1.5 hours.

A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) revealed plumes of blowing snow originating over northern Lake Winnipeg and southern Lake Manitoba, lofted by strong northerly winds in the wake of a cold frontal passage. The blowing snow originating over the southern portion of Lake Manitoba was then then channeled southward into the Red River Valley (topography), with horizontal convective roll clouds eventually developing.

In a sequence of MODIS Visible (0.65 µm) and Snow/Ice (1.61 µm) images from Terra and Aqua in addition to VIIRS Visible (0.64 µm) and Snow/Ice (1.61 µm) from NOAA-20 and Suomi NPP (below), the plumes of blowing snow were also easier to detect in the Snow/Ice images (due to better contrast against the existing snow cover).

Toggles between 250-meter resolution Terra/Aqua MODIS True Color and False Color RGB images (centered between Lake Manitoba and the North Dakota border) from the MODIS Today site (below) provided a more detailed view of the blowing snow streaming southeastward from Lake Manitoba into far northeastern North Dakota and far northwestern Minnesota.

GOES-17 “Red” Visible (0.64 µm) images (above) revealed the low-level circulation of an occluded Hurricane Force low (surface analyses) over the West Pacific Ocean on 09 January – 10 January 2019. This storm was forecast to produce wave heights up to 40-60 feet.

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) revealed the formation of a standing wave cloud along the Minnesota shoreline of Lake Superior on 08 January 2019. This cloud feature was formed by a vertically-propagating internal gravity wave that resulted from the interaction of strong post-frontal northwesterly flow with the topography of the shoreline — the terrain quickly drops from an elevation of about 2000 feet above sea level (over northeastern Minnesota) to about 600 feet above sea level (over Lake Superior) in a very short distance.

A northwest-to-southeast oriented cross section of RAP40 model fields along line segment B-B’ (below) showed a deep pocket of positive Omega (upward vertical motion, yellow to red colors) that corresponded to the cloud band along the Minnesota Lake Superior shoreline. Note that this Omega feature was vertically tilted in an “upshear” direction (toward the northwest), and extended upward to the 350-400 hPa pressure level. There was also an increasing upward component of the ageostrophic vertical circulation, which was likely the initial forcing mechanism leading to formation of the standing wave cloud seen on satellite imagery.

RAP40 model cross section along line B-B’ [click to play animation | MP4]